CN111758057A

CN111758057A - Optical connector with tilting mirror

Info

Publication number: CN111758057A
Application number: CN201980014474.2A
Authority: CN
Inventors: 米歇尔·A·哈泽; 郝冰
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2018-03-14
Filing date: 2019-03-01
Publication date: 2020-10-09
Anticipated expiration: 2039-03-01
Also published as: US20220357513A1; US11693185B2; US20210103098A1; JP2021517665A; US11402584B2; CN111758057B; WO2019175702A1

Abstract

The present disclosure relates to a light coupling unit for an optical connector including a waveguide alignment member that receives and aligns at least one optical waveguide. The light coupling unit includes a light redirecting member having an input surface configured to receive input light from an end face of the optical waveguide. The curved reflective surface of the light redirecting member receives light from the input surface that propagates along the input axis and redirects the light such that the redirected light propagates along a different redirection axis. An output surface of the light redirecting member receives the redirected light and transmits the redirected light as output light that propagates along an output axis and exits the light redirecting member. The curved reflective surface has a radius of curvature at a curved intersection with a first plane formed by the input axis and the redirecting axis. The curved reflective surface has an axis of rotation disposed in a first plane. The axis of rotation forms a non-zero first angle with the reorientation axis. The waveguide alignment member is configured such that the end face of the optical waveguide is positioned at a position that is not a geometric focal point of the curved reflective surface.

Description

Optical connector with tilting mirror

Background

The optical connector may be used for optical communication for a variety of applications, including: telecommunications networks, local area networks, data center links, and internal links in computer equipment. Expanded beams may be used in connectors for these applications to provide optical connections that are less sensitive to dust and other forms of contamination, and to allow alignment tolerances to be relaxed. If an expanded beam is present at the connection point, the optical connector is generally considered an expanded beam connector. Typically, the expanded beam is a beam having a diameter larger than the core of the associated optical waveguide (typically an optical fiber, such as a multi-mode optical fiber for multi-mode communication systems). The expanded beam is typically obtained by beam divergence from a light source or optical fiber. In many cases, the diverging beam is processed by an optical element, such as a lens or mirror, into an approximately collimated expanded beam. The expanded beam is then received by focusing the beam via another lens or mirror.

Disclosure of Invention

A light coupling unit for an optical connector includes a waveguide alignment member that receives and aligns at least one optical waveguide. The light coupling unit includes a light redirecting member having an input surface configured to receive input light from an end face of an optical waveguide. The curved reflective surface of the light redirecting member receives light propagating along an input axis from the input surface and redirects the light such that the redirected light propagates along a different redirection axis. An output surface of the light redirecting member receives the redirected light and transmits the redirected light as output light that propagates along an output axis and exits the light redirecting member. A curved intersection of the curved reflective surface and a first plane formed by the input axis and the redirection axis has a radius of curvature. The curved reflective surface has an axis of rotation disposed in the first plane. The axis of rotation forms a non-zero first angle with the reorientation axis. The waveguide alignment member is configured such that the end face of the optical waveguide is positioned at a position other than a geometric focal point of the curved reflective surface.

Drawings

Fig. 1 shows a schematic cross-sectional view of an optical connector according to some embodiments;

fig. 2A and 2B depict elliptical cross-sections of reflectors showing the relationship between geometric focal points and reflective surfaces, according to some embodiments;

fig. 3A shows a schematic cross-sectional view of a connector assembly according to an aspect of the present disclosure;

FIG. 3B shows a perspective schematic view of the optical path through the connector assembly of FIG. 3A;

FIGS. 4A and 4B are schematic diagrams illustrating ray tracing of a light coupling unit;

FIGS. 5A and 5B are schematic diagrams illustrating ray tracing of a portion of an exemplary light coupling unit, according to some embodiments;

FIG. 6A shows a schematic perspective view of an integral light coupling unit 600 according to one aspect of the present disclosure;

and is

Fig. 6B illustrates a schematic perspective view of a connector assembly according to one aspect of the present disclosure.

The figures are not necessarily to scale. Like numbers used in the figures refer to like parts. It should be understood, however, that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

Detailed Description

The present disclosure relates generally to single optical waveguides, groups of optical waveguides (such as optical fiber ribbons), and optical connectors that may be used to connect a single optical waveguide or multiple optical fibers such as in an optical fiber ribbon cable. The optical connectors discussed herein include an optical coupling unit that can combine features of optical waveguide alignment and redirection and shaping of optical beams. The optical connectors discussed in some embodiments are expanded beam connectors. In some embodiments, the light coupling unit is a unitary structure that may be a molded piece. The optical connector embodiments discussed herein may provide reduced insertion loss, reduced optical aberrations (such as coma), and/or reduced back reflection.

Fig. 1 illustrates a schematic cross-sectional view of an optical connector 190 according to some embodiments. The optical connector 190 includes at least one optical coupling unit 100 disposed within a housing 110. The cross-sectional view presented in fig. 1 is located on the XZ plane of the XYZ cartesian coordinate system such that the XZ plane passes through the central axis 122 of the optical waveguide 120.

The optical waveguide 120 is received and aligned by the waveguide alignment member 115 of the optical coupling unit 100. The optical waveguide 120 is received and aligned within the waveguide alignment member 115 such that the optical waveguide end face 124 faces the input surface 132 of the light redirecting member 130 of the light coupling unit 100. In some embodiments, the waveguide alignment member 115 is configured such that the end face 124 of the optical waveguide 120 is positioned at a location that is not a geometric focus of the curved reflective surface 134, as discussed in more detail below. In some cases, light redirecting member 130 may include a solid medium that is transparent to the wavelength of light input from optical waveguide 120 and has a refractive index greater than one. In some cases, the optical waveguide end face 124 can be proximate to the input surface 132 of the light redirecting member 130; in some cases, however, the optical waveguide end face 124 may be set back slightly from the input surface 132, for example, by using a waveguide stop feature (not shown). An index matching material may be disposed between waveguide end face 124 and input surface 132 to optically couple optical waveguide 120 to input surface 132. In some cases, the light redirecting member 130 may include a reflective surface that is a hollow cavity formed in the light coupling unit 110.

The optical connector 190 is configured to mate with a mating optical connector (not shown in fig. 1) along a mating direction. According to some aspects, the mating direction is not parallel to the central axis 122. To facilitate mating, the connector housing 110 also includes a mating surface 112 and alignment features 114, 116. The alignment features 114, 116 align the output surface 136 of the light redirecting member 130 within the optical connector to one of a second light coupling unit in a second optical connector (not shown) or a transceiver such as an optical detector or an emitter such as a Vertical Cavity Surface Emitting Laser (VCSEL). In a particular embodiment, the optional recessed mating surface 113 may be formed such that a pocket 160 may be formed adjacent the output surface 136 such that an air gap may be formed between the output surface 136 and an adjacent second optical connector or transceiver. In a particular embodiment, the integral light coupling unit 100 may be a male-female coupling unit, such that the first integral light coupling unit 100 and the second integral light coupling unit (not shown) may be identical and attached to each other, as described elsewhere. In a particular embodiment, at least one of the input surface 132 and the output surface 136 may include an anti-reflective coating and/or may be adjacent an index matching material.

Waveguide alignment member 115 may include a trench extending in a trench direction for receiving and aligning optical waveguides 120, as described, for example, in the following PCT publication nos.: WO2013/048730 entitled "OPTICAL CONNECTOR HAVING a PLURALITY of OPTICAL fibers with staggeredly cleaved ends COUPLED TO associated microlenses (OPTICAL CONNECTOR HAVING a planar OPTICAL fiber fiberes WITH STAGGERED CLEAVED ENDS couppled TO associated optofiber fibers"); WO2013/048743 entitled "OPTICAL SUBSTRATE HAVING a PLURALITY OF interleaved light redirecting FEATURES ON a MAJOR SURFACE THEREOF (OPTICAL SUBSTRATE HAVING a planar OF STAGGERED LIGHTREDIRECTING FEATURES ON a MAJOR SURFACE laser THEREOf"); and as described in the following U.S. patent application serial numbers: 61/652,478 (attorney docket No. 67850US002, filed 5/14/2013) entitled "OPTICAL INTERCONNECT (OPTICAL INTERCONNECT)" and 61/710,083 (attorney docket No. 70227US002, filed 9/27/2013) entitled "OPTICAL connector (OPTICAL INTERCONNECT)", which PCT publications and patent applications are incorporated herein by reference. In some cases, the groove direction may be parallel and aligned with the central axis 122. In some cases, waveguide alignment member 115 may instead include a cylindrical bore (not shown) capable of receiving and aligning optical waveguide 120, which may be an optical fiber. Optical waveguide 120 may be any suitable waveguide including, for example, a planar waveguide, a single mode fiber, or a multi-mode fiber. In some cases, optical waveguide 120 is a multimode optical waveguide suitable for wavelengths in the range of about 600 nanometers to about 2000 nanometers. In a particular embodiment, optical waveguide 120 can have a circular cross-sectional profile. In some cases, the optical waveguide may instead have a polygonal cross-sectional profile.

The light redirecting member 130 includes an input surface 132 for receiving input light 140 from the optical waveguide 120 along an input axis 142; a curved reflective surface 134 for reflecting the received input light 140 as redirected light 150 propagating along a different redirection axis 152; and an output surface 136 for receiving the redirected light 150 and transmitting the redirected light 150 as output light 155 propagating along an output axis 156. In some embodiments, input surface 132 may be a planar surface that is substantially perpendicular to input axis 142 and/or substantially parallel to reorientation axis 152. In some embodiments, output surface 136 may be a planar surface that is substantially parallel to input axis 142 and/or substantially perpendicular to redirection axis 152.

In fig. 1, the reorientation axis 152 is shown as lying within a first plane (i.e., the XZ plane) of the XYZ cartesian coordinate system, and the input axis 142 and the reorientation axis 152 form a reorientation angle Φ therebetween. The reorientation angle φ may be any desired angle suitable for the application, and may be, for example, greater than 90 degrees, or about 90 degrees, or less than 90 degrees, such as about 80 degrees, or about 70 degrees, or about 60 degrees, or about 50 degrees, or about 40 degrees, or about 30 degrees, or even less than about 30 degrees. In one particular embodiment shown in FIG. 1, the reorientation angle φ is about 93 degrees. In some cases, the central axis 122 of the optical waveguide 120 can coincide with the input axis 142; however, in some cases, optical waveguide 120 may be aligned to input surface 132 such that input axis 142 and central axis 122 form an angle (not shown) therebetween, as may be caused by refraction at the waveguide end face or the input surface of the optical coupling unit.

In some embodiments, rotational axis 106 is disposed at a first angle α 1 relative to input axis 142 and at a second angle α 2 relative to redirection axis 152 and/or output axis 156. In some cases, α 1 ≠ α 2, and in some cases, α 1 ≠ α 2. For example, α 1 and α 2 may be between about 40 degrees and about 50 degrees. In some implementations, α 1 ═ α 2 ═ 45 degrees. In some cases, when α 1 ═ α 2, the lowest aberration and lowest insertion loss are achieved.

In some embodiments, the output axis 152 may be oriented at a 90 degree angle relative to the input axis 142, as shown in fig. 1. In general, output axis 152 and input axis 142 may be oriented at angles other than 90 degrees to each other. The input light 140 has a first divergence half-angle θ i, wherein the first divergence half-angle θ i is between about 3 degrees and about 10 degrees, or between about 5 degrees and about 8 degrees, or about 7 degrees.

Redirected light 150 may be substantially collimated within light coupling unit 100. The redirected light 150 has a second divergence half-angle θ o, which in some cases may be a converging half-angle θ o, where the second divergence is less than the first divergence. In some cases, the second divergence or convergence half-angle θ o is less than about 5 degrees, or less than about 4 degrees, or less than about 3 degrees, or less than about 2 degrees, or less than about 1 degree.

In some cases, light exiting optical waveguide 120 that is received and aligned by waveguide alignment feature 115 propagates along the optical path from input surface 132 to output surface 136 such that redirected light 150 has a minimum beam size (e.g., cross-sectional area) that is located near output surface 136. For embodiments employing single mode waveguides, the beam waist (wait) of the redirected beam may be located near the output surface. In a particular embodiment, the input light 140 is a diverging beam and the redirected light 150 is a substantially collimated beam, which collimation is limited by the diffractive properties of the beam size.

The reflective surface 134 may be any suitable shape reflector capable of redirecting input light 140 having a first divergence into redirected light 150 having a second divergence less than the first divergence. In various embodiments, the curved reflective surface 134 may be, for example, an annular surface or an elliptical surface. The curved intersection of surface 134 with the XZ plane may be described or accurately approximated by an arc 134a having a radius of curvature "R" measured from the center 105 of arc 134 a. The arc center 105 lies on a line bisecting the redirection angle phi between the input axis 142 and the redirection axis 152. The surface 134 is further characterized by an axis of rotation 106, the axis of rotation 106 being disposed in the XZ plane and intersecting the input axis 142 at the geometric focus 108. Geometric focus 108 is a focus of an ellipse, a portion of which is best approximated by arc 134 a. Rotation axis 106 is non-parallel and tilted with respect to redirection axis 152 and/or output axis 156, as shown in fig. 1. For example, an annular or elliptical surface 134 may be created at a location where, for example, input axis 142 intersects surface 134 by rotating arc 134a (i.e., out of the XZ plane) about axis of rotation 106. The geometric focus 108 is an optical focal length f from the optical focus 107. The output surface 136 may be located one focal distance f from the intersection of the input axis 142 and the curved reflective surface 134.

Focal length f may be measured from focal point 107 to the intersection of input axis 142 and arc 134a, and is less than radius of curvature R, which may be characterized by the following expression:

where f is the optical focal length and phi is the internal angle between the input axis and the reorientation axis. For example, when angle Φ is 90 degrees (i.e., pi/2) and f is 0.60mm, R is 1.697 mm. In a particular embodiment, the light redirecting member 130 may be designed such that the path of the input light 140 and the redirected light 150 travels a combined distance of 2f from the waveguide end face surface 124 to the output surface 136.

The reflective surface 134 can be made reflective by including a reflective coating, such as, for example, a multilayer interference reflector (such as a bragg reflector) or a metal or metal alloy reflector (both of which can be suitable for use with the light redirecting member 130 being a solid material or a hollow cavity), as described elsewhere. In some cases, for a light redirecting member 130 that is a solid material, the reflective surface 134 may instead use Total Internal Reflection (TIR) to redirect the input light 140. To enable TIR to be effective, the connector housing 110 of the unitary light coupling unit 100 can further include an inner perimeter 119 at least partially surrounding the cavity 118, the inner perimeter 119 positioned such that the reflective surface 134 of the light redirecting member 130 can be protected from contamination that can frustrate TIR at the reflective surface 134, as known to those of skill in the art.

The light redirecting member 130 can be made of any suitable transparent and dimensionally stable material, including, for example, a polymer, such as polyimide. In one particular embodiment, the light redirecting member 130 can be made of a dimensionally stable transparent polyimide material, such as, for example, Ultem 1010 polyetherimide available from Saeber basic Innovation Plastics, Inc. of Pittsfield, Pittsfield MA, of Petzfeld, Mass, or Zeonex K26r cyclo olefin polymer available from Raynaud's Specialty Materials, San Jose, Calif. In some cases, optical waveguide 120 may be adhesively secured in a groove of waveguide alignment member 115. In a particular embodiment, an index matching gel or adhesive may be inserted between the light redirecting member 130 and the optical waveguide 120. By eliminating any air gaps in this region, refraction and fresnel losses can be reduced.

The center 105 of the arc may be located on a radius perpendicular to axis of rotation 106 and intersecting the redirection point of the central ray of input beam 140 and redirected beam 150, as shown in fig. 1. For example, the axis of rotation 106 intersects the input axis 142 at a point focal length behind the end face 124 of the optical waveguide 120.

The axis of rotation 106 of the curved reflective surface 134 is tilted with respect to the redirection axis 152 and/or the output axis 156. In addition, the waveguide alignment member is configured such that the end face 124 of the optical waveguide 120 is positioned at a location that is not the geometric focus 108 of the curved reflective surface 134. For example, in some embodiments, the end face 124 of the optical waveguide 120 can be located approximately midway between the curved reflective surface 134 and the geometric focus 108. This arrangement provides redirected light that is substantially collimated rather than substantially converging or diverging within the light coupling unit. As previously discussed, the redirected light 150 may have a second half angle of divergence or half angle of convergence θ o. In some cases, the second divergence or convergence half-angle θ o is less than about 5 degrees, or less than about 4 degrees, or less than about 3 degrees, or less than about 2 degrees, or less than about 1 degree.

The curved reflective surface 134 may be an inclined elliptical surface or an inclined annular surface that closely approximates an inclined elliptical surface, where inclination refers to the angle of inclination between the axis of rotation of the surface relative to the redirected beam axis 152 or the output beam axis 156. Fig. 2A depicts an elliptical cross-section of a reflector 200 showing the relationship between the eccentricity of the ellipsoid and the desired reflection angle phi. The eccentricity of an ellipse can be defined in terms of its major and minor axes (a and b) as:

in this design, the eccentricity depends on the desired reflection angle φ:

thus, for a 90 degree reflection (phi 90 degrees), the eccentricity should be such that

Fig. 2A and 2B depict elliptical cross-sections of the reflector showing the relationship between geometric focus 210 and reflective surface 234. Fig. 2B shows an elliptical cross-section of reflector 200, where light source 224 (e.g., an end face of the waveguide) is located at geometric focal point 295 of surface 234. The geometric focus 295 of the ellipsoidal surface 234 is located on the axis of rotation 206. FIG. 2B illustrates the convergence of reflected light when light source 224 is positioned at the geometric focus 295 of surface 234, as is characteristic of an ellipsoidal surface. Light emitted from the geometric focus 295 on the axis of rotation is reflected by the surface 234; the reflected light converges to a complementary geometric focus 295' on the axis of rotation 206.

In contrast, fig. 2A shows a situation where the light source 224 is not located at the geometric focus 295 on the axis of rotation 206, but is located one optical focal length from the surface 234 and one focal length away from the geometric focus 295. As shown in fig. 2A, when the light source 224 is not located at the geometric focus 295, but is located midway along the input axis between the geometric focus 295 and the surface 234, the reflected light is substantially collimated at the complementary focus 295'. The desired reflection angle 280 is controlled by selecting the appropriate angle of the axis of rotation relative to the input axis.

Fig. 3A illustrates a schematic cross-sectional view of a connector assembly 300 according to one aspect of the present disclosure. Each of the elements 100-160 shown in FIG. 3A corresponds to the previously described similarly numbered elements 100-160 shown in FIG. 1. For example, optical waveguide 120 of fig. 3A corresponds to optical waveguide 120 of fig. 1, and so on. In FIG. 3A, the connector assembly 300 includes a first unitary light coupling unit 100 and a second unitary light coupling unit 100 'coupled together such that the mating surfaces 112, 112' are adjacent to each other; alignment features 114 and 116 align with alignment features 116 'and 114', respectively; and the output surface 136 of the first unitary light coupling unit 100 is adjacent to and faces the output surface 136 'of the second unitary light coupling unit 100'. In fig. 3A, each of the first and second integrated light coupling units 100 and 100' is a male-female coupling unit that can be mated with each other to achieve a low-loss optical connection. The connector assembly 300 is configured such that light exiting the first optical waveguide 120 enters the second optical waveguide 120 ' after being redirected by the reflective surface 134 of the first unitary light coupling unit 100 and the reflective surface 134 ' of the second unitary light coupling unit 100 '.

The light exiting the first optical waveguide propagates a first propagation distance (f + f + f ' + f) between the waveguide end face 124 of the first optical coupling unit 100 and the end face 124 ' of the second optical coupling unit 100 ', the propagation distance (f + f + f + f) being substantially equal to twice the sum of the focal length f of the first and second integrated optical coupling units. In some cases, the focal length "f" of the first integrated light coupling unit 100 is substantially equal to the focal length "f" of the second integrated light coupling unit 100'. In some cases, the first optical waveguide 120 comprises a first multimode optical fiber and the second optical waveguide 120' comprises a second multimode optical fiber. In other cases, the first optical waveguide 120 comprises a first single mode optical fiber and the second optical waveguide 120' comprises a second single mode optical fiber.

Fig. 3B illustrates a perspective schematic view of a light path through the connector assembly 300 of fig. 3A obtained by ray tracing in accordance with an aspect of the present disclosure. In the embodiment shown in fig. 3B, the first and second reflective surfaces 134, 134' are right angle ring mirrors. In fig. 3B, first optical waveguide 120 injects first input light 140 that is reflected from first ring reflector 134 as first redirected light beam 150. The first redirected light beam 150 passes through the first output surface 136 of the first light redirecting member 130 and enters the second light redirecting member 130 ' through the second output surface 136 ' as a second redirected light beam 150 '. The second redirected light beam 150 'is reflected from the second annular reflector 134' as second input light 140 'into the second optical waveguide 120'.

The divergence of light rays 140 exiting the core of optical waveguide 120 represents the numerical aperture of the waveguide. Light propagates within the polymer of the light coupling unit and, for sufficiently large reflection angles phi, reflection can occur by total internal reflection. In a typical connector, light will propagate within a polymer (e.g., Zeonex K26r) and for sufficiently large angles (Φ, fig. 3A), reflection may occur by total internal reflection. The discs 136, 136' in the center of the model represent the interface between the two connectors.

Ray tracing has been used to calculate the component of insertion loss due to aberrations in an optical connector comprising a waveguide having a multimode 50 μm diameter fiber core. The slanted elliptical design and the annular design described herein provide lower insertion loss than previous connectors. Table 1 summarizes the calculated insertion loss due to 90 degree reflection and 600 μm focal length aberration.

TABLE 1

Design of	Insertion loss
		Paraboloid	0.53dB
Annular, axis parallel to the output beam	0.36dB
		Inclined ellipsoid	0.27dB
Inclined ring surface (45 degree)	0.24dB

It should be appreciated from table 1 that at wavelengths in the range of 600 nanometers to 2000 nanometers, the insertion loss due to aberrations of connector assemblies incorporating tilted reflectors according to embodiments discussed herein may be less than about 0.35dB, or less than about 0.325dB, or less than about 0.3dB, or less than about 0.275dB, or less than about 0.25 dB. The measured insertion loss of a connector assembly incorporating a tilted reflector according to embodiments discussed herein may be less than about 0.4 dB.

Low back reflection (return loss) is a property of high performance optical connectors and adapters. Previously designed physical contact connectors manage back reflection by providing an angled polished waveguide end face. Fig. 4A and 4B are schematic diagrams illustrating ray tracing with a typical prior design of the light coupling unit 400.

The input surface 432 of the light coupling unit 400 is nominally orthogonal to the central axis 422 of the optical waveguide 420. Index matching adhesive 484 is used to optically couple the angularly cleaved waveguide end face 424 to the input surface 432. However, reflection occurs because the light redirecting portion 421 of the light coupling unit 400 has a different index of refraction than the waveguide core or the adhesive. A large portion of the light reflected from the input surface 432 is coupled back into the waveguide core.

The curved reflective surface 434 redirects the input light toward the output surface 436. Despite the use of thin film anti-reflective coating 485, a small portion of the collimated redirected light at output surface 436 is reflected. Because collimated redirected light beam 491 impinges at normal incidence on output surface 486, a portion of collimated redirected light 491 can be reflected at output surface 436 and refocused back into waveguide 420 by curved reflective surface 434. Fig. 4A shows redirected light 491 that is projected at normal incidence on the input surface 432 and the anti-reflection (AR) coated output surface 436 of the light coupling unit 400. Fig. 4B shows that light from waveguide 420 is partially reflected back from both input surface 432 of light coupling unit 400 and AR-coated output surface 436. Solid line 499 and dashed line 498 represent two rays originating at opposite edges of the waveguide core. The reflected light, represented by solid line 489 and dashed line 488, is strongly coupled back into the waveguide 420, forming an inverted image of the core on the end face. These reflections at the input surface 432 and the output surface 436 may result in unacceptable back reflections in the waveguide.

In some embodiments, back reflection may be eliminated or significantly reduced by appropriately tilting the input surface and/or the output surface relative to the incident light, as shown in fig. 5A and 5B. Fig. 5A and 5B are schematic diagrams illustrating ray tracing of a portion of an exemplary light coupling unit 500, according to some embodiments.

As shown in fig. 5A and 5B, in some embodiments, the normal 532' to the input surface 532 is at an angle Φ with respect to the axis 522 of the optical waveguide 520. Thus, the central ray of light reflected by the input surface 532 is reflected at an angle of 2 Φ with respect to the waveguide axis 522. Assuming that the binder 584 is index matched to the waveguide core, if all of the reflected light falls outside the numerical aperture of the waveguide, the reflected light will not couple significantly back into the waveguide core. That is, if Φ > Θ_NAWherein Θ is_NAIs the angle associated with the numerical aperture of the fiber: theta_NAAsin (NA/n core), and wherein NA is the numerical aperture of the fiber, and n core isRefractive index of the waveguide core. For example, in some embodiments, Φ > 9 degrees. According to some embodiments, the input surface 532 is angled relative to the axis 522 of the optical waveguide 520 such that less than about 1% of the light reflected by the input surface 532 is coupled back into the waveguide 520.

The angled input surface 532 need not be planar, for example, the input surface 532 may be spherical, cylindrical, toroidal, or other useful lens shape, provided that the angular extent of the surface relative to the optical axis of the waveguide reduces or prevents reflections back into the waveguide core. For example, in some embodiments, substantially all (e.g., greater than about 80%, greater than about 85%, or greater than 90%, or greater than 99%) of the input light reflected by the input surface 532 is reflected at an angle relative to the waveguide axis that is greater than the numerical aperture angle of the optical waveguide 520. For example, in some embodiments, less than 20%, less than 15%, or less than 10% of the light reflected by the input surface 532 is coupled into the core of the optical waveguide 520.

Although not shown in fig. 5A and 5B, an anti-reflective coating and/or anti-reflective nanostructures may be applied to the input surface 532 to reduce reflections at the interface between the adhesive 584 and the light coupling unit 500.

Additionally or alternatively, the approach of the total internal reflection lens formed by the curved reflective surface 534 may be designed as described above to redirect and collimate the light 578 from the optical waveguide 520 such that the redirection axis 552 of the redirected light (the redirection axis 552 is located along the path of the central ray of the redirected light) is at an angle Θ relative to the normal 536' of the output surface 536 of the light coupling unit 500. Thus, any light reflected from output surface 536 is refocused by TIR lens 534 to a point away from the waveguide core. Thus, substantially all of the light reflected by the output surface 536 and focused by the TIR lens 534 falls outside the core of the waveguide 520 and is therefore not coupled back into the waveguide. For example, about 80%, about 85%, or about 90% of the light reflected by output surface 536 and refocused by TIR lens 534 falls outside the core of the waveguide. According to some embodiments, less than 10% or even less than 1% of the redirected light reflected by the output surface 536 is refocused by the curved reflective surface 534 into the core of the waveguide 520.

In fig. 5B, solid line 599 and dashed line 598 represent two rays originating at opposite edges of the waveguide core. For a smaller Θ, the reciprocal image of the waveguide core is centered at a distance s of 2f Θ from the waveguide axis 522 as the core center, where f is the focal length of the TIR lens and Θ is expressed in radians. The redirected light, represented by solid line 589 and dashed line 588, is reflected by the output surface 536 and focused by the curved reflective surface 534 to a point at a distance s from the center of the core of the waveguide 520. To reduce the coupling of this reflected image back into the waveguide core, the distance s should be greater than the diameter D of the waveguide core (or fiber mode). In some embodiments, the angle of incidence Θ is greater than D/2f and greater than about 2.5 degrees.

A coupled optical coupling unit pair incorporating these angled input and output surfaces may achieve return loss values of 45dB, 55dB, or even better at 1310 nm.

In the embodiments described herein, the output surface 536 need not be planar, for example, the output surface 536 may be spherical, cylindrical, toroidal, or other useful lens shape, provided that the angular extent of the surface 536 relative to the axis of the output beam reduces or prevents reflection back into the waveguide core.

Selecting non-zero angles of incidence at the input and output surfaces may involve adjusting the design of the light coupling unit to accommodate the associated refraction of the transmitted light. At the input surface, this refraction is generally negligible due to the index-matching adhesive. At the output surface, ray tracing techniques may be used to take into account the angle at which the refracted beam enters the air.

FIG. 6A shows a schematic perspective view of an integral light coupling unit 600 according to one aspect of the present disclosure.

Each of the elements 600-630 shown in FIG. 6A corresponds to the previously described similarly numbered elements 100-130 shown in FIG. 1. For example, optical waveguide 620 of fig. 6A corresponds to optical waveguide 120 of fig. 1, and so on. In fig. 6A, a plurality of optical waveguides 620 are received and aligned by the waveguide alignment member 615 to guide light from the optical waveguides to a light redirecting member 630 within the connector housing 610. The light coupling unit 610 includes alignment features 614, 616.

Fig. 6B illustrates a schematic perspective view of a connector assembly 603 according to one aspect of the present disclosure. The connector assembly 603 may be similar to those multi-fiber connector assemblies shown, for example, in U.S. patent application serial No. 61/652,478 (attorney docket No. 67850US002, filed 5/14/2013) entitled "OPTICAL INTERCONNECT",

this patent application provides a compact, reliable optical interconnect; however, the light redirecting member 630 of the present invention provides advantages of a multi-fiber connector assembly not previously understood. According to one aspect of the present disclosure, the connector assembly 603 includes a first optical connector 601 having a first integral light coupling unit 600 and a second optical connector 601 'having a second integral light coupling unit 600'. Each of the first and second integrated light coupling units 600 and 600' may be male and female connectors, as described elsewhere. The first and second optical connectors 601, 601 ' may be protected and supported by the first and second connector frames 602, 602 ', which may enable a more reliable mating of the respective first and second alignment features 614, 616, 614 ', 616 ' of each of the integrated light coupling units 600, 600 '.

Each of the multi-fiber connector assemblies may be adapted to be interconnected using a variety of connection schemes, as known in the art, as further described, for example, in the following co-pending PCT publications: WO2013/048730 entitled "OPTICAL connector HAVING a PLURALITY OF OPTICAL fibers with staggeredly cleaved ends coupled TO ASSOCIATED MICROLENSES" (OPTICAL connector HAVING a fiber side OF OPTICAL fibers WITH STAGGERED CLEAVED end coated led TO ASSOCIATED MICROLENSES); WO2013/048743 entitled "OPTICAL SUBSTRATE HAVING a PLURALITY of interleaved light redirecting FEATURES ON a MAJOR SURFACE THEREOF (OPTICAL SUBSTRATE HAVING a PLURALITY of interleaved light redirecting FEATURES a planar optics oriented LIGHT REDIRECTING featureon a MAJOR SURFACE THEREOF)"; and as further described in the following U.S. patent application serial nos.: 61/652,478 entitled "OPTICAL interconnect (OPTICAL interconnect)" (attorney docket No. 67850US002, filed 5/14/2013) and 2561/710,083 entitled "OPTICAL CONNECTOR (OPTICAL CONNECTOR)" (attorney docket No. 70227US002, filed 9/27/2013).

The items described in the present disclosure include:

item 1. a light coupling unit for an optical connector, comprising:

a waveguide alignment member configured to receive and align at least one optical waveguide; and

a light redirecting member comprising:

an input surface configured to receive input light from an end face of the optical waveguide;

a curved reflective surface configured to receive light from the input surface that propagates along an input axis and redirect the light received from the input surface, the redirected light propagating along a different redirection axis; and

an output surface configured to receive the redirected light from the curved reflective surface and transmit the redirected light received from the output surface as output light that propagates along an output axis and exits the light redirecting member, a curved intersection of the curved reflective surface and a first plane formed by the input axis and the redirection axis having a radius of curvature, the curved reflective surface having an axis of rotation disposed in the first plane, wherein the axis of rotation forms a first angle with the redirection axis, the first angle being non-zero, and the waveguide alignment member being configured such that the end face of the optical waveguide is positioned at a location that is not a geometric focus of the curved reflective surface.

Item 2. the light coupling unit of item 1, wherein the axis of rotation is disposed at a second angle relative to the input axis, and the first angle and the second angle are equal.

Item 3. the light coupling unit of item 2, wherein the first angle and the second angle are about 45 degrees.

Item 4. the light coupling unit of item 2, wherein the first angle and the second angle are in a range of about 40 degrees to about 50 degrees.

Item 5 the light coupling unit of item 2, wherein the first angle and the second angle are about 43.5 degrees.

Item 6. the light coupling unit of any one of items 1 to 5, wherein the curved surface is an annular surface.

Item 7. the light coupling unit of any one of items 1 to 5, wherein the curved surface is an elliptical surface.

Item 8. the light coupling unit of any of items 1 to 7, wherein a second divergence of the reflected light along the redirection axis is less than a first divergence of the input light along the input axis.

Item 9. the light coupling unit of any one of items 1 to 8, wherein the axis of rotation is disposed at one optical focal length f measured from the input surface along the input axis and at two focal lengths measured from the curved reflective surface measured along the input axis, the focal lengths being less than the radius of curvature.

Item 10 the light coupling unit of item 9, wherein the radius of curvature R is:

where φ is the angle between the input axis and the reorientation axis.

Item 11 the light coupling unit of item 9, wherein the output surface is disposed at a focal distance measured from the curved reflective surface along the reorienting axis.

Item 12. the light coupling unit of any one of items 1 to 11, wherein the light coupling unit is a unitary structure.

Item 13. the light coupling unit of any one of items 1 to 12, wherein the input surface is substantially perpendicular to the input axis.

Item 14. the light coupling unit of any one of items 1 to 12, wherein the input surface is substantially perpendicular to the output surface.

Item 15. the light coupling unit of any one of items 1 to 14, wherein an angle between the input axis and the reorientation axis is less than 90 degrees.

Item 16. the light coupling unit of any of items 1 to 14, wherein an angle between the input axis and the reorientation axis is greater than 90 degrees.

Item 17. the light coupling unit of any of items 1 to 14, wherein an angle between the input axis and the reorientation axis is about 93 degrees.

Item 18. the light coupling unit of any one of items 1 to 17, wherein the curved reflective surface reflects the light received from the input surface by total internal reflection.

Item 19. the light coupling unit of any one of items 1 to 18, wherein the input surface is angled relative to an axis of the optical waveguide.

Item 20. the light coupling unit of any one of items 1 to 19, wherein the input surface is angled relative to an axis of the optical waveguide such that substantially all input light reflected by the input surface is reflected at an angle relative to the waveguide axis that is greater than a numerical aperture angle of the waveguide.

Item 21. the light coupling unit of any one of items 1 to 20, wherein the input surface is angled relative to an axis of the optical waveguide such that less than about 1% of the light reflected by the input surface is coupled back into the waveguide.

Item 22. the light coupling unit of any of items 1 to 20, wherein the input surface is angled relative to an axis of the optical waveguide such that input light reflected by the input surface is reflected by an angle Φ, wherein Φ is greater than a numerical aperture angle Θ of the optical waveguide_NAAnd Φ is greater than 9 degrees.

Item 23. the light coupling unit of any one of items 1 to 22, wherein a redirection axis of the redirected light is at an angle Θ > D/2f relative to a normal to the output surface, where D is a diameter of a core of the waveguide and f is a focal length of the curved reflective surface.

Item 24. the light coupling unit of any of items 1 to 22, wherein a redirection axis of the redirected light is at an angle Θ > D/2f and Θ > 2.5 degrees relative to a normal to the output surface, where D is a diameter of a core of the waveguide and f is a focal length of the curved reflective surface.

Item 25. the light coupling unit of any of items 1 to 24, wherein the redirected light reflected by the output surface is focused by the curved reflective surface to a point at a distance s from a center of a core of the waveguide, and s > D, where D is a diameter of the core of the waveguide.

Item 26 the light coupling unit of any of items 1 to 25, wherein less than about 10% of the redirected light reflected by the output surface is refocused by the curved reflective surface into the core of the waveguide.

Item 27. the light coupling unit of any of items 1 to 25, wherein less than about 1% of the redirected light reflected by the output surface is refocused by the curved reflective surface into the core of the waveguide.

Item 28. a light coupling unit for an optical connector, comprising:

a light redirecting member comprising:

an output surface configured to receive the redirected light from the curved reflective surface and transmit the redirected light received from the output surface as output light that propagates along an output axis and exits the light redirecting member, a curved intersection of the curved reflective surface and a first plane formed by the input axis and the redirection axis having a radius of curvature, the curved reflective surface having an axis of rotation disposed in the first plane, wherein the axis of rotation is not parallel to the redirection axis, and wherein the waveguide alignment member is configured such that the end face of the optical waveguide is positioned approximately midway between the curved reflective surface and a geometric focus of the curved reflective surface.

Item 29. a light coupling unit for an optical connector, comprising:

a light redirecting member comprising:

a curved reflective surface configured to receive light from the input surface that propagates along an input axis and reflect the light received from the input surface, the reflected light propagating along a different redirection axis; and

an output surface configured to receive light from the curved reflective surface and transmit the light received from the output surface as output light that propagates along an output axis and exits the light redirecting member, a curved intersection of the curved reflective surface and a first plane formed by the input axis and the redirecting axis having a radius of curvature, the curved reflective surface having an axis of rotation disposed in the first plane, wherein the axis of rotation is not parallel to the redirecting axis, and wherein the redirected light has a redirected divergence half angle or convergence half angle θ o that is less than about 5 degrees.

Item 30. an optical connector, comprising:

a connector housing: and

the at least one light coupling unit of claim 1, wherein the optical connector is configured to mate with a mating optical connector along a mating direction that is non-parallel to the input axis.

Item 31. a connector assembly comprising:

the first light coupling unit of item 1 having at least one first light waveguide received and aligned by the waveguide alignment member of the first light coupling unit, the first light coupling unit mated with the second light coupling unit of claim 1 having at least one second light waveguide received and aligned by the waveguide alignment member of the second light coupling unit, the output surface of the first light coupling unit adjacent to and facing the output surface of the second light coupling unit, the connector assembly configured such that light exiting the first light waveguide enters the second light waveguide after propagating through the light redirecting members of the first and second light coupling units.

Item 32. the connector assembly of item 31, wherein light exiting the first optical waveguide propagates a first propagation distance between the input surface of the first light coupling unit and the input surface of the second light coupling unit, the propagation distance being substantially equal to twice a sum of the focal length of the first light coupling unit and the focal length of the second light coupling unit.

Item 33. the connector assembly of any of items 31-32, wherein the focal length of the first light coupling unit is substantially equal to the focal length of the second light coupling unit.

Item 34. a connector assembly comprising:

the first light coupling unit of claim 1 having at least one first multimode optical fiber received and aligned by the waveguide alignment member of the first light coupling unit mated with the second light coupling unit of claim 1 having at least one second multimode optical fiber received and aligned by the waveguide alignment member of the second light coupling unit, the output surface of the first light coupling unit adjacent to and facing the output surface of the second light coupling unit, the connector assembly configured such that light exiting the first optical waveguide enters the second optical waveguide after propagating through the light redirecting members of the first and second light coupling units, wherein at a wavelength in the range of 600 to 2000 nanometers, an optical insertion loss of the connector assembly due to the aberration is less than about 0.3 dB.

Item 35 the connector assembly of item 33, wherein the optical insertion loss due to aberrations is less than about 0.275 dB.

Item 36 the connector assembly of item 33, wherein the measured optical insertion loss is less than about 0.4 dB.

Item 37. a light coupling unit for an optical connector, comprising:

a light redirecting member comprising:

an output surface configured to receive light from the curved reflective surface and transmit the light received from the output surface as output light that propagates along an output axis and exits the light redirecting member, a curved intersection of the curved reflective surface with a first plane formed by the input axis and the redirecting axis having a radius of curvature, the curved reflective surface having an axis of rotation disposed in the first plane, wherein the input surface is angled with respect to an axis of the optical waveguide such that substantially no input light reflected by the input surface is coupled into the waveguide.

Item 38 the light coupling unit of item 37, wherein the input surface is angled relative to an axis of the optical waveguide such that input light reflected by the input surface is reflected by an angle Φ, wherein Φ is greater than a numerical aperture Θ of the optical waveguide_NAAnd Φ is greater than 9 degrees.

Item 39. the light coupling unit of any one of items 37 to 38, wherein the input surface is angled relative to an axis of the optical waveguide such that less than about 20% of the input light reflected by the input surface is coupled back into the optical waveguide.

Item 40. the light coupling unit of any one of items 37-39, wherein the input surface is angled relative to an axis of the optical waveguide such that less than about 5% of the input light reflected by the input surface is coupled back into the optical waveguide.

Item 41. the light coupling unit of any one of items 37-39, wherein the input surface is angled relative to an axis of the optical waveguide such that less than about 1% of the input light reflected by the input surface is coupled back into the optical waveguide.

Item 42. a light coupling unit for an optical connector, comprising:

a light redirecting member comprising:

an output surface configured to receive light from the curved reflective surface and transmit the light received from the output surface as output light that propagates along an output axis and exits the light redirecting member, a curved intersection of the curved reflective surface with a first plane formed by the input axis and the redirecting axis having a radius of curvature, the curved reflective surface having an axis of rotation disposed in the first plane, wherein the output light is at an angle Θ relative to a normal to the output surface such that substantially all light reflected by the output surface and refocused by the curved reflective surface falls outside of a core of the waveguide.

Item 43 the light coupling unit of item 42, wherein the redirection axis is angled relative to the output surface normal such that about 80% of the light reflected by the output surface and focused by the curved reflective surface falls outside the core of the waveguide.

Item 44. the light coupling unit of item 42, wherein the redirection axis is angled relative to the output surface normal such that about 85% of the light reflected by the output surface and focused by the curved reflective surface falls outside the core of the waveguide.

Item 45 the light coupling unit of item 42, wherein the redirection axis is angled relative to the output surface normal such that about 90% of the light reflected by the output surface and focused by the curved reflective surface falls outside the core of the waveguide.

Item 46. the optical coupling unit of any one of items 42 to 45, wherein Θ > 2.5 degrees.

Item 47. the light coupling unit of any of items 42 to 46, wherein the redirection axis is at an angle Θ > D/2f relative to the output surface normal, wherein D is a diameter of a core of the waveguide and f is a focal length of the curved reflective surface.

Item 48 the light coupling unit of item 47, wherein the redirected light reflected by the output surface is focused by the curved reflective surface to a point at a distance s from a core center of the waveguide, wherein s-2 f Θ.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

Various modifications and alterations to the embodiments described above will be apparent to those skilled in the art, and it should be understood that this disclosure is not limited to the illustrative embodiments set forth herein. Unless otherwise indicated, the reader should assume that features of one disclosed embodiment are also applicable to all other disclosed embodiments. It should be understood that all U.S. patents, patent applications, patent application publications, and other patent and non-patent documents cited herein are incorporated by reference to the extent they do not contradict the foregoing disclosure.

Claims

1. A light coupling unit for use in an optical connector, the light coupling unit comprising:

a light redirecting member comprising:

2. The light coupling unit of claim 1, wherein the axis of rotation is disposed at one optical focal length, f, measured from the input surface along the input axis and at two focal lengths measured from the curved reflective surface along the input axis, the focal lengths being less than the radius of curvature.

3. The light coupling unit of claim 2, wherein the radius of curvature R is:

where φ is the angle between the input axis and the reorientation axis.

4. The light coupling unit of claim 1, wherein the input surface is angled relative to an axis of the optical waveguide such that substantially all input light reflected by the input surface is reflected at an angle relative to the waveguide axis that is greater than a numerical aperture angle of the waveguide.

5. A light coupling unit for use in an optical connector, the light coupling unit comprising:

a light redirecting member comprising:

6. A light coupling unit for use in an optical connector, the light coupling unit comprising:

a light redirecting member comprising:

7. A connector assembly comprising:

the first light coupling unit of claim 1 having at least one first light waveguide received and aligned by the waveguide alignment member of the first light coupling unit, the first light coupling unit mated with the second light coupling unit of claim 1, the second light coupling unit having at least one second light waveguide received and aligned by the waveguide alignment member of the second light coupling unit, the output surface of the first light coupling unit adjacent to and facing the output surface of the second light coupling unit, the connector assembly configured such that light exiting the first light waveguide enters the second light waveguide after propagating through the light redirecting members of the first and second light coupling units.

8. A connector assembly comprising:

9. A light coupling unit for use in an optical connector, the light coupling unit comprising:

a light redirecting member comprising:

an output surface configured to receive light from the curved reflective surface and transmit the light received from the output surface as output light that propagates along an output axis and exits the light redirecting member, a curved intersection of the curved reflective surface and a first plane formed by the input axis and the redirecting axis having a radius of curvature, the curved reflective surface having an axis of rotation disposed in the first plane, wherein the input surface is angled with respect to an axis of the optical waveguide such that substantially no input light reflected by the input surface is coupled into the waveguide.

10. A light coupling unit for use in an optical connector, the light coupling unit comprising:

a light redirecting member comprising:

an output surface configured to receive light from the curved reflective surface and transmit the light received from the output surface as output light propagating along an output axis and exiting the light redirecting member, a curved intersection of the curved reflective surface and a first plane formed by the input axis and the redirecting axis having a radius of curvature, the curved reflective surface having an axis of rotation disposed in the first plane, wherein the output light is at an angle O relative to a normal to the output surface such that substantially all light reflected by the output surface and refocused by the curved reflective surface falls outside of a core of the waveguide.